Tnt-tetraborate gelled aqueous explosive slurry



the laboratory to the commercial stage.

United States Patent 3,108,917 TNT-TETRABGRATE GELLED AQUEGEE EXPLQMVESLURRY John Douglas Mclrvine, St. Hilaire, Quebec, tCanada, assignor toCanadian Industries Limited, Montreal,

Quebec, Canada, a corporation of Canada No Drawing. Filed Apr. 9, 1962,Ser. No. 185,835 Claims priority, applieationCanada July 3, 1961 4Claims. (Cl. 149-105) This invention relates to the recently discoveredslurr-ied blasting explosives which consist of an organic explosive andone or more inorganic oxidizing salt-s, slurr-ied in a saturated aqueoussolution of said salts. Thus water, in an amount between about 8% and26% by weight, is an essential ingredient of such explosives.

In Canadian Patent No. 617,006, there are disclosed sluiried blastingagents of the aforesaid type containing about 8% to 26% of water, 15% to35% of particulate trinitrotoluene and from 0.1% to 1.0% of agel-forming mannogalaotan, the remainder being substantially alloxidizing salt such as ammonium nitrate optionally mixed with up to 50%of sodium nitrate and minor amounts of other nitrates, chlorates andperchlorates. it is also disclosed in'the said patent that the inclusionin the slurries of mannogalactans, e.g. guar gum or carob seed gum,gives gelled slurries which are highly resistant to water. The gelledslurries may thus be poured gently into water and still remain coherent,and the resulting immersed masses are resistant to the ingress of waterand to the leaching of the inorganic salts.

It is further disclosed in the above patent that a critical amount ofborax may be added to the mannogalactancontaining slurries to give muchmore cohesive gels. It is believed that the bora-te ions in the boraxcross-link the manno-galactan-thickened slurries to give greatlyimproved cohesiveness, md indeed a borax-eontaining slurry may bedropped from a considerable height into water and still retain itsshape. These cross-linked slurries thus constitute extremely desirableexplosives which are safe, powerful and much more water resistant thanexplosives such as ammonium nitrate/fuel oil mixtures, yet much moreeasily handled than waterproof packaged explosives. Furthermore, theproblem of segregation of the particulate species is solved by the boraxaddition, even when the packaged explosives are subjected to varyingambient temperatures.

However, while ordinary borax (Na B O 10H O') gives a satisfactorycohesive gelled slurry on a laboratoryscale, it has been found that itis not possible on an industrial scale to produce the best and mostdesirable of the laboratory products using ordinary borax. The reasonsfor this are as follows. Firstly, if the borax and the mannogalacten areadded to the slurry at the same time, they interact and themannogalactan is rendered incapable of swelling, no gel at all beingproduced and still'less therequired cohesive gel. It is thus necessaryto allow the mannogalactan to .pre-gel the salt solution for a lengthyperiod of time before adding the borax which is inconvenient and reducesproduction. Secondly, once the borax is added, the slurry gel becomesfirmer and more cohesive so quickly that it 'soon cannot flow, and it isthus difficult to package it without'the inclusion of air pockets,

whereas the slurry without the borax can cheaply and easily be pumped orpoured into packages.

It has now been discovered that certain fused'or glassy metallictetraborates, in a substantially anhydrous state, can replace the boraxin the slurry with the great advantage that the gelling thereof isdelayed. This improvement enables a very desirable explosive to advancefrom The fused tetra- "ice borates can be used in such an amount thatthe ultimate gel strength is the optimum, but this strength may bededeveloped up to 24 hours after mixing. Thus, immediately after mixing,the cohesiveness of the gel is quite low and the explosive slurry may bepumped, handled and packaged very readily. In order to achieve the bestbalance between low initial viscosity and final gelled strength, itisdesirable that the fused glassy metallic tetraborates be present in aconcentration, calculated as B 0 of from 2% to 10% by weight of themannogalactan.

It is thus an object of this invention to provide an improved readilymanufa'otured cohesive gelled blasting explosive wherein water is anessential ingredient, which :is nevertheless highly water resistant inuse. A further object is to provide a process for manufacturing such anexplosive wherein the attainment of the cohesive gel is delayed for sometime after all the ingredients are mixed, in order that the explosivecan be handled and packaged in the fluid state. Additional objects willappear hereinafter.

In accordance with this invention, therefore, in an explosive blastingagent of the kind comprising an aqueous slurry of at least one oxidizingsalt and a granular waterinsensitive organic explosive, said slurrybeing at least partially gelled with a mannogalactan, there is providedthe improvement which comprises the presence in said slurry of a fused,glassy metallic tetrabora-te in a concentration, calculated as B 0 offrom 2% to 10% by weight of the mannogalaotan.

This improved blasting agent is prepared by mixing all the ingredientstogether, packaging the resultant slurry While .in the partially gelledstate and allowing the packaged material to stand for at least 24 hourswhereby a fully gelled cohesive slurried explosive is obtained.

In a preferred embodiment, the improved explosive of the inventionconsists essentially of a cohesive gelled aqueous slurry of at least oneoxidizing salt and a granular Water-insensitive organic explosive, saidslurry con- .taining from 8% to 26% by weight of water, from 15% to 40%by weight of the organic explosive, from 0.1% to 2.0% by weight of agel-forming mannogalactan andfrom 0.002% to 0.2% by weight, calculatedas B 0 of a fused, glassy metallic tetraborate, the remainder beingsubstantially all oxidizing salt.

A very suitable oxidizing salt for inclusion in the improved explosivesof this invention is ammonium nitrate. It is in some cases advantageousto replace some or all, suitably up to 50%, of the ammonium nitrate bysodium nitrate whereby a denser explosive results. Additionally, thechlorates and perchlorates of sodium and ammonium are excellentoxidizing salts, although less safe than the nitrates. The potassiumsalts are equally useful and are included within the scope of theinvention, although they are at present more expensive than. the sodiumsalts. Mixtures of all these species may beused, together with minoramounts of other metallic nitrates, chlorates and perchlorates. Theparticle size of the oxidizing salts is not critical.

The organic explosives suitable for use in the irnproved blastingagents. of this invention are described herein as granular and waterinsensitive.

By granular, it is intended to exclude liquid explosive such asnitroglycerine and nitroglycerol, and to indicate that the explosivesshould be in powdered or particulate form. Three very suitableexplosivesare trinitrotoluene (TNT), composition B (a mixture of a major part,viz. about 60% by weight, of RDX which is cyclotrimethylenetrinitramineand a minor part, viz. about 40% by weight, of TNT plus a little Wax)and smokeless powder. The latter is a solid material and consists ofcolloided nitrocellulose, with the addition, in the socalled doublebased powders, of up to 40% nitroglycerine. All these explosives arebest used in the particulate form, i.e. in fairly large grains, such asgrains coarser than a size 30 Tyler mesh. It is now known, however, thatfine granular material can be used but there is a certain loss ofsensitivity in small diameter charges. In addition, a large class oforganic explosives which can be made in the granular form is suitablefor use in this invention but, in many cases, these explosives provemore expensive than the preferred three above-mentioned. This classincludes pentaerythritol tetranitrate (PETN), tetryl, RDX and pentolite(a mixture of about equal parts of TNT and PETN) By water insensitive,it is meant that the explosibility of the organic explosives and theirgranular form must not be affected by water in small amounts. Thus, forexample, uncolloided nitrocellulose or nitrostarch are unsuitable sincethey readily absorb water to form a mat, and are then insensitive todetonation.

The fused, glassy metallic tetraborates suitable for use in the improvedexplosive and process of this invention are made by fusion of the morecommon powdered, generally hydrated forms. This fusion may be conductedby any heating means, and generally requires a temperature of 600 C. to1000 C. The result is glassy granules which should be ground before use;a particle size between 8 and +30 Tyler mesh is suitable but notcritical. However, not more than A; of the material should be fines,i.e. through 50 mesh. The following metallic tetraborates are suitable:lithium, sodium, potassium, magnesium, calcium and barium tetraboratesand mixtures thereof. However, the cationic or metallic constitutent haslittle effect upon the efficiency of the fused tetraborates in thisinvention, and any metallic tetraborate capable of assuming the glassyform upon fusion, and having at least some solubility in water, issuitable. Furthermore, the tetraborate need not be pure. There areseveral suitable materials sold for fertilizer use, such as Rasorite andFertilizer Borate 65 of the U5. Borax Chemical Corp., and Pyrobor of theAmerican Potash and Chemical Corp. The former is described as aconcentrated sodium tetraborate ore product containing 94-97% anhydroussodium tetraborate and less than 1% (typically 0.4%) of water. Otherfertilizing products are probably less pure. For this reason, andbecause of the different molecular weights of the various metallictetraborates, the amounts of these materials to be included in theexplosive of the present invention are defined herein on the basis ofthe contained amount of B That is, for example, a material containingone gram of calcium tetraborate contains only 0.72 gram calculated as B0 The order of mixing the ingredients in the process of this inventionis not critical, and excellent products can be made by comparativelycrude procedures. Any type of stirred mixing vessel may be used, but asteam heated mixer wherein the action is a gentle folding, combined witha lifting of material from the bottom of the vessel to the top, ispreferred. The ingredients may be added in any order, but due to thenegative heat of solution of ammonium nitrate, it is preferred that hotwater be used when this ingredient is present in a large proportion. Ina preferred procedure, half the inorganic salt is added first, then thewater, then the other half of the salt with the mannogalactan premixedtherein. Finally, the granular organic explosive and the glassy metallictetraborate are premixed and added to the thickened salt slurry. By thismethod, the mannogalactan is allowed to swell for a while before thegranular explosive is added. This helps the explosive to becomedistributed throughout the slurry and to minimize settling, particularlywhen a minimum amount of mannogalactan is used. The addition of theglassy borate last gives the greatest possible time during which theslurry can be packaged before the extremely cohesive stage is reached.

The following Examples illustrate the products and process of thepresent invention but the scope of the in vention is not to berestricted to the details described. The gelled slurried explosives may,for example, additionally contain other materials normally used inexplosives, including metallic powders, ammonium picrate, cellulosicpulps and other similar species.

EXAMPLE 1 The following mixing procedure was used to manufacture a largebatch of the blasting explosive of this invention, a heated ribbon mixerbeing used.

300 lbs. of ammonium nitrate and 200 lbs. of sodium nitrate were Weighedinto the empty mixer and the steam heat was then turned on and 192 lbs.of hot water added and mixed in. Meanwhile, a further 300 lbs. ofammonium nitrate and 200 lbs. of sodium nitrate were weighed out, and 8lbs. of guar gum roughly mixed into the solids, which were then added tothe mixer. Then 217 grams of Rasorite, a proprietary fused, glassysodium tetraborate, were added to 400 lbs. of pelleted TNT, and thewhole added to the now thickened slurry. As soon as the composition washomogeneous, it was dumped to a hold tank, and thence dropped by gravityinto polythene bags. After 24 hours the explosive had become cohesive;it would no longer flow as a fluid, but rather on inversion of a bag,the whole body would fall out as a plastic mass, necking down andseparating cleanly from the polythene bag. If dropped into water, themass did not separate or diffuse, but sank as a cohesive body. It canthus be seen that a material of remarkable properties, particularlysuitable for field use as a blasting agent, is produced by the method ofthis invention.

Furthermore, the blasting explosive detonated unconfined in a 2 inchdiameter tube, using a gram pentolite booster. It was extremelypowerful, having a density of 1.55 g./cc. and a borehole pressure of66,700 atm., but was quite insensitive to shock, friction, or even ablasting cap.

EXAMPLE 2 Since the viscosity of the slurried blasting agents isditficult to measure, due to their inhomogeneity, a laboratoryexperiment was performed to show the delayed gelling of the fusedtetraborates. A Brookfield rotational viscometer was used to measure theincrease of viscosity of 60% ammonium nitrate solution containing threesets of additives, namely 1.0% guar gum,

1.0% guar gum plus 0.03% Rasorite, and 1.0% guar gum plus 0.03% boraxadded after 15 minutes.

The contents of both borates were calculated as B 0 The results aregiven in Table I.

Table l 60% NH4NO3, 60% NH4NO:, 60% NHANOS, 1.0% guar, 1.0% guar, Time1.0% guar, cp. 0.03 0.03% borax Rasorite, op. added at 15 minutes, cp.

The borax was added 15 minutes late to prevent segregation and this isthe only possible way to use it on a plant scale. However, itimmediately gelled the slurry, and it can be seen that in the criticalperiod, 1 to 2 hours after mixing, when the slurry must be packaged, theRasorite slurry is only slightly more viscous than that thickened byguar alone, whereas the borax has given a much higher viscosity. Inaddition the improvement in final (24 hrs.) gel strength by the use of aboratc is shown.

EXAMPLE 3 :Slurriecl explosives were made from the followingingredients:

Sodium chlorate--- percent by weight" 62. 4. 44. 2 Flaked TNT -do 25.034. 8 Guar gnm do 0. 6 0. 63 Water do 12.0 19. 8 Fertilizer borate(impure fused glassy sodium tetraborate) pereent by weight" 0.02 0.02

The resulting slurries slowly gelled over 24 hours with no segregation,to give strong cohesive gells that would separate cleanly from theirpolythene bags. The explosive power of the gelled slurry was measured bythe ballistic pendulum, to give a so-called Triton value ('I NT=10.0).The Triton value of A was 8.5 that of B was 9.5.

EXAMPLE 4 Two blasting agents were made up wherein the organic explosiveconsisted of a mixture of TNT and a rifle type smokeless powder. (Thispowder consisted of 89.5% nitrocellulose gelled by 9.7% clinitrotoluene,and 0.4% dibutylphthalate.) The formulae and properties of the blastingagents were:

Ammonium nitrate percent by weight 53. 61. 5 Sodium nitrate... o 9.0 1.0Smokeless powder cdo. 12. 5 18. 75 TNT (flake) 10 12.5 6.25 Guar gum."do- 0.5 O. 5 Water do 12.0 12.0 Fused sodium tetraborat'x d0 0. 02 0. 02

(as B203) (as 13203) V.O.D. 4 diam it./sec 4, 390 4, 520 Triton Value10.8 10. 0

The samples on which the velocities of detonation (V.O.D.) were measuredwere primed with a pentolite primer of 160 g. weight. Other effectiveblasting agents were prepared using no TNT and 28% to 38% smokelesspowder. The latter agent had the formula:

Ammonium nitrate 29.0% by weight. Sodium nitrate 19.4% by weight.Smokeless powder 38.0% by weight. Guar gum 0.6% by weight. Water 13.0%by weight. Fertilizer borate 0.02% by weight (as B 0 V.O.D. at 1 /2"diam 5380 ft./sec.

EXAMPLE 5 Apart from the tetraborate, the composition was that ofExample 1.

Table II Viscosity (in arbitrary units) alter- Fused, glassy tetrnboratehr. 1 hr. 2 hrs. 3V hrs. 24 hrs.

184 293 453 508 520 255 349 622 151 269 394 458 628 224 394 583 l, 178878 573 1,080 NazBtO1 209 328 442 421 1, 330 Fertilizer grade sodiumtetraborate 168 266 382 1, 090

What I claim is:

1. An improved explosive blasting agent consisting essentially of acohesive gelled aqueous slurry of at least one inorganic salt, granulartrinitrotoluene, a gel-forming mannogala'ctan and a substantiallyanhydrous fused glossy metallic tetraborate in a concentrationcalculated as B 0 of from 2% to 10% by weight of said mannogalactan, theparticle size of at least /8 of said tetraborate being larger than a 50Tyler mesh.

2. An improved explosive blasting agent consisting essentially of acohesive gelled aqueous slurry containing from 8% to 26% by weight ofwater, from 15% to 40% by weight of granular trinitrotoluene, from 0 .1%to 2% by weight of a gel-forming mannogalactan and from 0.002% to 0.2%by weight, calculated at B 0 of a substantially anhydrous fused, glossymetallic tetraborate, the remainder being substantially all inorganicoxidizing salt, the particle size of at least of said tetraborate beinglarger than a 50 Tyler mesh.

3. An improved process for making a cohesive gelled slurried blastingagent which comprises mixing together water, at least one inorganicoxidizing salt, granular trinitrotoluene, a gel-forming mannogalactanand a substantially anhydrous fused, glossy metallic tet'raborate in anamount, calculated as B 0 of from 2% to 10% by weight of saidmannogalactan, the particle size of at least /8 of said tetraboratebeing larger than a 50 Tyler mesh.

4. An improved process for making a cohesive gelled slurried blastingagent which comprises mixing together from 8 to 26 parts by weight ofwater, from 15 to 40 parts by weight of granular trinitrotoluene, from0.1 to 2.0 parts by weight of a gel-forming mannogalactan, from 0.002 to0.2 part by weight, calculated as B 0 of a sub stantially anhydrousfused glossy metallic tetraborate, the particle size of at least of saidtetraborate being larger than a 50 Tyler mesh, and sufficient inorganicoxidizing salt to make a total of 100 parts by weight.

References Cited in the file of this patent UNITED STATES PATENTS868,636 Braunstein Oct. 22, 1907 2,063,572 Woodburry Dec. 8, 19362,358,384 Davis Sept. 19, 1944 2,733,139 Winning Jan. 31, 1956 2,768,073Davidson Oct. 23, 1956 2,839,374 Taylor et al June 17, 1958 2,847,291Sakurai Aug. 12, 1958 2,860,041 Griflith Nov. 11, 1958 2,867,172 HradelIan. 6, 1959 3,037,417 Andrew et a1 June 5, 1962 3,049,043 Milani Aug.14, 1962 3,072,509 Barnhart Jan. 8, 1963

1. AN IMPROVED EXPLOSIVE BLASTING AGENT CONSISTING ESSENTIALLY OF A COHESIVE GELLED AQUEOUS SLURRY OF AT LEAST ONE INORGANIC SALT, GRANULAR TRINITROTOLUENE, A GEL-FORMING MANNOGALACTAN AND A SUBSTANTIALLY ANHYDROUS FUSED GLOSSY METALLIC TETRABORATE IN A CONCENTRATION CALCULATED AS B2O3, OF FROM 2% TO 10% BY WEIGHT OF SAID MANNOGALACTAN, THE PARTICLE SIZE OF AT LEAST 7/8 OF SAID TETRABORATE BEING LARGER THAN A 50 TYLER MESH. 